UV radiation is a spectrum of invisible rays that are part of the energy produced by the sun. There are two kinds of UV radiation: UVA and UVB. UVB radiation is well known for causing sunburn, and scientists believe these rays cause most skin cancers, including squamous cell carcinoma.UVA is the dominant tanning ray and, according to the National Cancer Institute, may also cause skin damage that can lead to premature aging and skin cancer.

Squamous cell carcinoma is more likely to occur in people who have been exposed to intermittent bursts of UV radiation — UVB, in particular — especially when the exposure results in sunburn and blistering. People who work outdoors, spend a lot of time at the beach, or regularly participate in outdoor sports have a greater risk of developing skin cancer. UVA rays can even travel through glass and clouds. Sun lamps and tanning beds, are another source of exposure to harmful UVA rays and should be avoided.

Fair Skin

People with fair skin — especially those with blond or red hair and blue or light-colored eyes — are more likely to develop skin cancer. (A propensity to freckle or sunburn can be a warning sign.) The skin of these particularly at-risk individuals contains less of the pigment melanin, which provides a degree of natural protection from the sun. People with dark skin, however, can still develop squamous cell carcinoma. In fact, these skin cancers make up more than two thirds of cancers diagnosed in individuals of African descent.

Personal History of Skin Cancer

People who have had skin cancer are more likely to develop skin cancer again.

Precancerous Skin Conditions

Although the majority of actinic keratoses do not become cancerous, squamous cell carcinomas can occasionally arise from these lesions. Leukoplakia and Bowen’s disease can also be precursors to these cancers.

Exposure to Industrial Compounds

Repeated exposure to radiation, and exposures to coal tar, arsenic, or other industrial compounds, can raise a person’s risk of squamous cell carcinoma.

Weakened Immune System

People with a weakened immune system are also at an increased risk for developing squamous cell carcinoma. Examples would include patients with lymphoma and leukemia, on chemotherapy, or treated with drugs to prevent organ transplant rejection.

Age

A long latency period usually occurs between exposure to harmful UV radiation and the development of squamous cell carcinoma, putting older people at a greater risk. This risk also grows as people grow older because the body loses its ability to repair DNA damage over time.

Other Risk Factors

Smoking: A history of smoking can significantly increase the risk of developing an oral squamous cell carcinoma.

Human papillomavirus (HPV): The same HPVs that are associated with cervical cancer can also lead to squamous cell carcinomas. These often develop around the fingernail.

Chronic ulcers: Squamous cell carcinomas can arise within chronic ulcers, a phenomenon known as a Marjolin ulcer.

Long-term burn scars: A squamous cell carcinoma is the most common type of cancer that can develop on a burn scar.

Psoriasis treated with PUVA and UVB: A combination of psoralen and UVA light is an effective treatment for psoriasis. However, its use can lead to an increased risk of squamous cell carcinoma. UVB light is another common therapy for this skin condition, and can also result in a higher risk of these cancers.

Prevention

The best way to prevent skin cancer is to protect yourself and your family from excessive exposure to sunlight — and not only when you go to the beach. Skin cancer prevention should be practiced every day by seeking shade, wearing protective hats and clothing, avoiding the midday sun and tanning beds, and using a broad-spectrum sunscreen (one that protects against UVA and UVB rays), even on cloudy days. Look for an SPF of at least 30, and apply two thin coats (about an ounce per application) as part of your daily routine. Be sure to reapply every two hours if swimming or sweating.

Screening and Skin Examination

Doctors at Memorial Sloan Kettering do not recommend regular screening for non-melanoma skin cancer. However, any suspected skin cancer should be brought to the attention of a physician or dermatologist immediately.

Diagnosing and treating squamous cell carcinoma as early as possible minimizes the risk of serious cosmetic damage and maximizes the chance of a cure. It is particularly important to identify these cancers early, because a small percentage metastasize, or spread to other organs.

During a skin examination with a dermatologist, the doctor will usually look at new growths, spots, or bumps on the patient’s skin to determine whether they might be cancerous or precancerous. After the examination, the doctor will show the patient how to examine his or her own skin and determine whether any growths have changed in appearance. Patients may want to pay particular attention to moles that have an asymmetrical shape, an uneven border, more than one color, or appear to be growing. This visual inspection should cover the entire surface of the skin, including places where the sun may not even shine: the scalp, the soles of the feet, and between the toes.